By now most Yukoners are probably at least somewhat aware that Yukon River Chinook salmon are in trouble.
In recent years, the population has suffered from an unheard of population collapse driven by stressors such as historical over harvest, habitat destruction, and the impacts of an ever warming planet.
All this has led conservation officials in both the Yukon and Alaska to declare a seven year moratorium on harvesting Chinook Salmon as conservation organizations on both sides of the border have raced to understand why the fish are disappearing in a bid to return the once mighty summer salmon runs to the Yukon River.
While much of this work has focused on obvious factors such as those described above, the cause of the collapse is still not well understood with no one single smoking gun reason for the decline.
As a result scientists have begun turning their eyes outward, searching for additional stressors throughout the salmon’s ecosystem and beyond. For researchers at the Yukon First Nations Salmon Stewardship Alliance, this has meant turning their eyes to a relatively unknown and almost completely un-researched species; the Rainbow Trout.
Rainbow Trout are considered a non-native species across most of the Yukon with only a few native populations found around the Kathleen and Aishihik watersheds around Haines Junction according to the Yukon Department of the Environment.
Several introductions of Rainbow Trout into other Yukon waters occurred throughout the later half of the 20th century with the majority of today’s non-native spawning populations tracing their lineage to introductions sometime in the 1950s.
While many of these populations are in isolated lakes where they are cut-off from spreading to the wider ecosystem, one population living in the waters of the Louise Lake and McIntyre watershed is causing some concern among some salmon conservation researchers.
According to Elizabeth MacDonald, Manager of Fisheries Natural Resources and Implementation at the Yukon First Nations Salmon Stewardship Alliance, these trout could threaten juvenile Chinook Salmon in the nearby Yukon River.
Belonging to the same salmonid family of fish species, the freshwater dwelling Rainbow Trout are broadly similar to juvenile Chinook Salmon and the two species often prey upon the same food sources. According to MacDonald this can pose a problem for the Chinook who are often out competed for food by the trout.
“As those larger rainbows move through the system, we do see the juvenile chinook move off,” said MacDonald. “So there’s definitely the potential for competition, and I’m sure it’s happening.”
In addition to out competing the Chinook for food, Rainbow Trout can also pose an additional threat as a conduit for diseases. Given the two species broad similarities and similar habitats the risk of trout passing on pathogens such as the potentially devastating Whirling Disease represents a significant risk to juvenile Chinook.
Despite all these risk factors and the historical precedence for Rainbow Trout to find their way into Chinook habitats, the body of scientific knowledge about the non-native rainbows is relatively small with only a few studies being done on the fish in the last several decades.
Seeing this blind spot in the knowledge along with the trout’s potential risk to the embattled Chinook, a team of researchers at YFNSSA took it upon themselves to fill in the blind spot and launched a new study program to better understand the trout population and its potential effects.
Working on a shoestring budget, the team began their research in the summer of 2025 trapping and removing small numbers of rainbow from lakes and streams around the Whitehorse area and recording their findings.
Now in its second year the program aims to create a broader understanding of how the trout population is changing over time in order to better understand the risk factor they pose to the ecosystem and lay the groundwork for a potential removal in the future.
The News joined several YFNSSA staff in the field during the second week of August as the team undertook several days of fieldwork trapping and removing some invasive trout.
First going out on a Monday morning, staff from YFNSSA set up 10 fish traps and a fyke net in
a creek just above Louise Lake.
The team first started by assembling and baiting the fish traps with scraps of salmon wrapped in a cheese cloth tied to the inside of the traps.
Consisting of a wire mesh cylinder with an inverted cone on either end the live catch traps are dead simple. Each cone on the traps has a hole at the bottom allowing curious or hungry trout to enter the trap but making it almost impossible for the fish to find their way back out. Upon retrieval the traps can be separated into two halves to retrieve any fish caught.
Once all the traps were assembled, and baited, the team donned rubber hip waiters and PFDs before setting off for the creek.
Working their way methodically upstream Fisheries Biologists, Wes Moir and Marina Milligan placed the traps in a variety of areas such as calm deep pools along the banks of faster running water where trout often hang out. Each trap was also secured to a tree branch or other anchor point on land to ensure all the traps set would still be in place when the team returned the following day.
Once all the traps were set in place, the team also staked a fyke net across the mouth of the creek hoping to catch any trout that bypassed the traps upstream. Moirexplained that setting up traps in a wide variety of areas and varying the catchment method with the addition of the Fyke net gave the researchers the best chance at catching trout as well as other fish species which would aid the team in understanding the overall ecology of the aquatic ecosystem.
Upon return the following day the team followed much of the same procedure as the day before. This time Moir was joined by MacDonald.
The pair started by pulling the Fyke net at the bottom of the creek which no trout and a couple of Slimy Sculpin, a small bottom dwelling fish native to the Yukon. Working their way upstream from the fyke net, Moir and MacDonald waded through chilly yet crystal clear creek water to retrieve the traps and hopefully some trout inside.
The first several traps were duds prompting remarks about previous field days that had yielded zero trout and a joke that the rainbows may be feeling a bit camera shy in the presence of an additional interloper.
However, the team’s luck soon turned with the third trap yielding several rainbow trout including a fairly large fish measuring just over 10 centimetres in length, a good size for this small stream.
More jackpots soon followed with several more traps yielding additional rainbows as well as a few more Slimy Sculpin and a sole Arctic Grayling.
Once the fish had all been collected and safely transferred into a large 5-gallon water bucket Moir and MacDonald brought them back to their processing station on the tailgate of their pickup truck.
Since rainbow trout are an invasive fish that can cause harm to native species this was a one way trip for rainbows. After a quick observation of the live rainbows in a fish viewing device, the fish were quickly and humanely killed with a swift blade through the spinal cord before being processed further.
Once dispatched the fish were measured and weighed with their measurements noted alongside the location they were caught.
The sex of the fish was also determined through a field dissection to find their reproductive organs which are entirely internal. On this particular day every rainbow caught was found to be a male with several suspected to have reached reproductive maturity.
Once all the fish had been processed the carcasses were returned to the creek so that their nutrients would continue to support life in the watershed with the carcasses serving as a food source for native species.
While the removal and recording of barely more than half a dozen fish may seem like a small effort to some, MacDonald said the goal isn’t to remove the trout completely but to lay the groundwork for future work by advancing the scientific understanding of this trout population.
“We’re not putting a big dent in it right now but we’re really trying to find that window for sexual maturity, because then you can find out when they’re naturally spawning, and know the time period when you could target them on spawning grounds,” said MacDonald.
MacDonald said her team hopes that advancing this knowledge will pave the way for another organization with greater resources for larger scale projects such as a full removal will grab the baton in the future.
“Our hope is that just by doing this, somebody else with more capacity will be like, ‘Hey, this is a problem. Let’s do something about it,’ and will take it on,” said MacDonald. “At least we’ve taken those first initial steps and progressed the knowledge and the plan for how we could potentially attempt to remove them or at least reduce their numbers so they’re not spreading and have less of an impact on Chinook.”
Contact reporter Noah Korver at noah.korver@yukon-news.com
By Noah Korver, Local Journalism Initiative Reporter
Original Published on Aug 14, 2026 at 10:40
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